Interleaving data over frames communicated in a wireless channel

ABSTRACT

A mobile communications system includes a radio access network, such as an Enhanced General Packet Radio Service (EGPRS) network, in which mobile stations are able to enter into a discontinuous transmission (DTX) mode. During DTX mode of a first mobile station that is allocated a channel portion (e.g., a time slot of a frame), the radio access network is able to multiplex traffic from another mobile station onto the same channel portion. A mechanism is provided to enable the first mobile station to send a request for re-allocation of the channel portion. The request includes a real-time fast access associated control channel (RTFACCH) resource request message (RTRRM). In response to the RTRRM, the radio access network sends an RTFACCH resource assignment message (RTUAM). An interleaving scheme is also provided for half-rate mobile stations, in which one set of traffic frames are interleaved over plural bursts according to a first algorithm and a second set of traffic frames are interleaved over plural bursts according to a second algorithm.

CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of U.S. Ser. No. 09/715,787, filed Nov. 17, 2000,which is hereby incorporated by reference.

TECHNICAL FIELD

This invention relates generally to communicating data over a wirelesschannel.

BACKGROUND

Mobile communications systems, such as cellular or personalcommunications services (PCS) systems, are made up of a plurality ofcells. Each cell provides a radio communications center in which amobile station establishes a call with another mobile station orwireline unit connected to a public switched telephone network (PSTN).Each cell includes a radio base station, with each base stationconnected to a base station controller or mobile switching center thatcontrols processing of calls between or among mobile stations or mobilestations and PSTN units.

Various wireless protocols exist for defining communications in a mobilenetwork. One such protocol is a time-division multiple access (TDMA)protocol, such as the TIA/EIA-136 standard provided by theTelecommunications Industry Association (TIA). With TIA/EIA-136 TDMA,each channel carries a frame that is divided into six time slots tosupport multiple (3 or 6) mobile stations per channel. Other TDMA-basedsystems include Global System for Mobile (GSM) communications systems,which use a TDMA frame divided into eight time slots (or burst periods).

Traditional speech-oriented wireless systems, such as the TIA/EIA-136and GSM TDMA systems, utilize circuit-switched connection paths in whicha line is occupied for the duration of the connection between a mobilestation and the mobile switching center. Such a connection is optimumfor communications that are relatively continuous, such as speech.However, data networks such as local area networks (LANs), wide areanetworks (WANs), and the Internet use packet-switched connections, inwhich communication between nodes on a communications link is by datapackets. Each node occupies the communications link only for as long asthe node needs to send or receive data packets. Popular forms ofcommunications over packet-switched networks include electronic mail,web browsing, text chat sessions, file downloads, and other types ofdata transfers.

Several packet-switched wireless connection protocols have been proposedto provide more efficient connections between a mobile station and adata network. One such protocol is the General Packet Radio Service(GPRS) protocol, which complements existing GSM systems. Anothertechnology that builds upon GPRS is the Enhanced Data Rate for GlobalEvolution (EDGE) technology, which offers even higher data rates. Theenhancement of GPRS by EDGE is referred to as Enhanced GPRS (EGPRS).Another variation of EGPRS is the COMPACT technology. GPRS, EGPRS, andCOMPACT are established by the European Telecommunications StandardsInstitute (ETSI).

The packet-switched wireless connection protocols provide efficientaccess to data networks, such as the Internet, LANs, WANs, and the like.A growing use of such data networks is for voice and other forms ofreal-time or streaming communications (such as video, audio and video,multimedia, and so forth). Various protocols have been defined to enablesuch real-time or streaming communications over the data networks, withone popular type of packet-switched network being the Internet Protocol(IP) network.

In some wireless communication systems, mobile stations are able toenter into a discontinuous transmission (DTX) mode. When a mobilestation is not transmitting, such as when a user is not talking, andthere is no other traffic to communicate, the mobile station can enterinto DTX mode to save power and also to reduce interference with othermobile stations. During DTX, a channel between the mobile station andthe base station is idle (that is, no traffic is being communicated).However, other mobile stations do not have access to the idle channel,since the channel is dedicated to the voice user. This is to ensure thatthe voice user can quickly start communicating over the channel once theuser resumes talking. As a result, available bandwidth is wasted in somemobile communications systems.

SUMMARY

In general, according to one embodiment, a system for use in a mobilecommunications network comprises a wireless interface adapted to receivetraffic over a wireless channel portion from a first mobile stationinvolved in half-rate communications. A controller is adapted to receivean indication that the first mobile station has entered discontinuoustransmission mode and to multiplex traffic from a second mobile stationonto the wireless channel portion while the first mobile station is indiscontinuous transmission mode.

In general, according to another embodiment, a method of interleavingdata over a plurality of frames comprises interleaving the dataaccording to a first algorithm over plural frames communicated over awireless channel for a first set of data; and interleaving the dataaccording to a second algorithm over plural frames communicated over thewireless channel for a second set of data.

Some embodiments of the invention may include one or more of thefollowing advantages. Bandwidth of channel portions in a wirelesscommunications system is increased by multiplexing traffic from anothermobile station when a first mobile station has stopped transmittingreal-time, interactive traffic (e.g., voice), such as duringdiscontinuous transmission (DTX) mode. A reliable mechanism is providedto ensure that the first mobile station can quickly gain access back tothe channel portion if the first mobile station starts transmittingagain. This may be particularly useful when the traffic communicated bythe first mobile station includes voice or other forms of real-time,interactive data. An interleaving scheme of data from half-rate mobilestations enable an efficient multiplexing of data from another mobilestation while the half-rate mobile station is in DTX mode.

Other features and advantages will become apparent from the followingdescription, from the drawings, and from the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an embodiment of a mobile communicationssystem.

FIG. 2 illustrates multiplexing of traffic transmitted by first andsecond mobile stations, in accordance with an embodiment.

FIG. 3 is a message flow diagram of messages exchanged between, andactions performed by, a mobile station and a base station, in accordancewith one embodiment.

FIGS. 4A-4B and 5A-5B illustrate multiframes for carrying traffic andcontrol signaling between the mobile station and the base station, withstatistical multiplexing illustrated for traffic of a half-rate mobilestation that has entered DTX mode and of another mobile station.

FIGS. 6A-6B and 7A-7B illustrate multiframes for carrying traffic andcontrol signaling between the mobile station and the base station, withstatistical multiplexing illustrated for traffic of a full-rate mobilestation that has entered DTX mode and of another mobile station.

FIGS. 8A-8B are a block diagram of components of the communicationssystem of FIG. 1.

FIG. 9 illustrates a message transmitted by a first mobile station afterexiting discontinuous transmission (DTX) mode to request allocation ofthe traffic channel portion that has been allocated to a second mobilestation.

FIG. 10 illustrates an uplink assignment message to assign the channelportion back to the first mobile station.

FIG. 11 is the flow diagram of a process performed by a base station, inaccordance with an embodiment.

FIG. 12 illustrates the communications of a resource request message atdifferent times and the communications of the responsive uplinkassignment messages, in accordance with an embodiment.

FIG. 13 is a block diagram of a circuit to detect for the resourcerequest message, in accordance with one embodiment.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present invention. However, it will beunderstood by those skilled in the art that the present invention may bepracticed without these details and that numerous variations ormodifications from the described embodiments may be possible.

Referring to FIG. 1, a mobile communication system 10, which may be acellular or a personal communications services (PCS) system, includes aradio access network (RAN) 11 that includes base stations 12 havingtransceivers to transmit and receive radio frequency (RF) signals. Thebase stations 12 are coupled to a system controller 50, with each basestation controlling communications with mobile stations in respectivecells, cell sectors, or other cells segments. Examples of mobilestations that can communicate with the RAN 11 over RF channels includemobile telephones, mobile computers, personal digital assistants (PDAs),and other types of mobile stations.

In one embodiment, the radio access network 11 is an EGPRS (EnhancedGPRS or General Packet Radio Service) network that is able to supportpacket-switched data services. Alternatively, the radio access networkmay be a GPRS or an COMPACT network, or other types of wireless networksthat are capable of supporting packet-switched data services, includinga code-division multiple access (CDMA) network. The GPRS, EGPRS, andCOMPACT protocols are set by the European Telecommunications StandardsInstitute (ETSI). As used here, reference to a “GPRS system” or “GPRSnetwork,” refers to any one of the GPRS, EGPRS, and COMPACT systems ornetworks.

In the GPRS network 11, the system controller 50 is a serving GPRSsupport node (SGSN), which is connected to the base station 12 over aIu-ps interface. The SGSN 50 is also coupled to a gateway GPRS supportnode (GGSN) 52 over a Gn interface, which forms the gateway between theradio access network 11 and a packet-based data network 54, such as theInternet. Various network devices (not shown), such as a networktelephone, a computer system, an Internet appliance, and so forth, arecoupled to the packet data network 54. Some of the network devices arecapable in participating in a real-time, interactive call session (e.g.,a voice session, video conferencing session) with a mobile stationthrough the radio access network 11. In addition, the packet datanetwork 54 may be coupled through a gateway system 56 to a publicswitched telephone network (PSTN) 58, which is coupled to wirelinetelephones. Each mobile station is also capable of participating in avoice call session with the wireline telephone through the radio accessnetwork 11, packet data network 54, gateway system 56, and PSTN 58.

A “real-time, interactive” communications session refers to an exchangeof data, such as audio and/or video data, on a substantially real-timebasis between two terminals. A session is substantially real-time ifinteraction is occurring between two endpoints or parties, with acommunication from one end point followed relatively quickly by aresponse or another communication from the other endpoint, typicallywithin seconds, for example. Any substantial delay in the transmissionof frames or packets carrying information associated with real-time,interactive communications may result in perceived degradation of thequality of the communications or in the reliability of thecommunications.

One type of packet-switched communications includes communicationsaccording to the Internet Protocol (IP). One version of IP is describedin Request for Comments (RFC) 791, entitled “Internet Protocol,” datedSeptember 1981; and another version of IP is described in RFC 2460,entitled “Internet Protocol, Version 6 (IP v6 Specification)”, datedDecember 1998. Packet-switched networks such as IP networks communicatewith packets, datagrams, or other units of data over networks. Unlikecircuit-switched networks, which provide a dedicated end-to-endconnection or physical path for the duration of a communicationssession, a packet-switched network is based on a connectionless,internetwork layer. Routing of packets is based on destination addressescarried in the packets. The packets may be transmitted along differentpaths, and thus, may arrive at a destination in an order that isdifferent than the transmission order. The destination terminalreassembles the received packets.

As shown in FIG. 1, mobile stations 34 and 40 are performing voicecommunications. In the example, the voice communications is referred toas VoIPoEGPRS (voice over IP over EGPRS), which refers to voice carriedin IP packets that are in turn carried in EGPRS frames between themobile stations and the radio access network 11. Instead of voice, themobile stations 34 and 40 are also capable of communicating other typesof real-time, interactive data, such as video data, multimedia data, andso forth. The mobile stations 34 and 40 can be half-rate or full ratemobile stations.

The mobile stations 34 and 40 associated with voice or other real-time,interactive users, communicate with the radio access network 11 overwireless channels 18, 20, 22, 24, 26, 28, 30, and 32. The other mobilestations in the illustrated example include mobile stations 36 that arereceiving electronic mail, mobile stations 38 that are transmittingelectronic mail, and mobile stations 42 that are performing web browsingcommunications. Channels 14 and 16 are indicated as being available forother users.

As used here, a “channel portion” or “wireless channel portion” refersto a time slot of a frame transmitted on a given channel having apredetermined frequency. In a TDMA system such as an EGPRS system, eachframe is divided into multiple time slots (e.g., 8 in the EGPRS system).For full-rate users, each time slot is allocated to carry bearer trafficof a mobile station. For half-rate users, each time slot is allocated tocarry bearer traffic of two mobile stations. In other embodiments, thechannel portion can be a portion of another type of channel, such as achannel in a code-divisional multiple access (CDMA) system.

To enhance the bandwidth for communications with the various mobilestations in the radio access network 11, multiplexing of traffic isperformed when the mobile stations 34 and 40 (associated with voice orother real-time, interactive data users) are in discontinuoustransmission (DTX) mode and thus not transmitting traffic. When thatoccurs, the radio access network 11 allocates the channel portion thatis used by the voice user mobile station (currently in DTX mode) toanother mobile station, such as one of mobile stations 36, 38, and 42(which are communicating packet traffic) or to another mobile stationthat is communicating real-time, interactive data or streaming data.

On the downlink path, multiplexing of plural mobile stations, even ifone is a voice user, is relatively simple to implement since the basestation is aware of the traffic that needs to be transmitted downlink.However, in the uplink path, to provide adequate performance, amechanism in accordance with some embodiments is provided to enable thevoice user mobile station to request the channel portion that has beenrelinquished to another mobile station while the voice user mobilestation is in DTX mode. The time between the request and there-allocation of the channel portion is relatively small to ensure thatvoice traffic is not substantially delayed. The mechanism to enable therequest and assignment of a channel portion for a mobile station exitingDTX mode includes a Real-Time Fast Access Associated Control Channel(RTFACCH), as further described below.

Thus, using the RTFACCH mechanism, an on-demand feature is provided tothe voice user mobile station for requesting re-allocation of a channelportion (e.g., time slot) that has been allocated to another mobilestation during DTX mode of the voice user mobile station. The requestfor re-allocation can be transmitted in any frame (with certainexceptions) after the voice user mobile station detects that it hasexited DTX mode. Thus, the voice user mobile station does not need towait for a pre-assigned frame or block before it can send someindication that it has exited DTX mode and is ready to startcommunicating traffic again. Typically, allocation of blocks forcommunication of traffic is performed using either USF (Uplink StateFlag), which is transmitted on the downlink path, or in an RRBP(Relative Reserved Block Period) field, also transmitted on the downlinkpath. In fact, the voice user mobile station can transmit the requestfor re-allocation of the time slot during a period in which the othermobile station is transmitting traffic. As a result, mechanismsaccording to some embodiments are provided to detect the request despitethe collision with traffic from the other mobile station on the sametime slot (or channel portion).

In one embodiment, the radio access bearers of the GPRS network 11include four different traffic classes (e.g., quality of service or QoSclasses), including conversational traffic class, streaming trafficclass, interactive traffic class, and background traffic class. The mainfactor that distinguishes these traffic classes from each other is howsensitive to delay they are. For example, the conversational trafficclass includes traffic that is the most sensitive to delay, while thebackground traffic class includes traffic that is least sensitive todelay. Conversational and streaming traffic classes are primarilyintended to be used for real-time traffic flows. The conversationaltraffic class includes real-time, interactive traffic, such as Internettelephony, while the streaming traffic class includes real-time traffic,such as transmissions of audio, video, or multimedia files that arebeing downloaded from a website to a terminal. Interactive andbackground traffic classes are primarily intended for use withnon-real-time traffic flows, and include traffic flows associated withelectronic mail, web browsing, file transfers, and so forth.

In the example of FIG. 1, mobile stations 34 and 40 are communicatingtraffic that are in the conversational traffic class, while mobilestations 36, 38, and 42 are communicating traffic that are in theinteractive or background traffic class.

Referring to FIG. 2, multiplexing of traffic data from two mobilestations 100 and 102 on the same channel portion is illustrated. In oneexample, the mobile station 100 is communicating conversational classtraffic, while the mobile station 102 is communicating interactive orbackground class traffic. However, in other examples, the mobilestations 100 and 102 may communicate other types of traffic.

As shown in FIG. 2, the mobile station 100 is communicating voice datawith periods of silence (104, 106, and 108) corresponding to DTX mode ofthe mobile station 100 during which the user of the mobile station 100is not speaking. During the silent periods 104, 106, and 108, data(represented as 110, 112, and 114) from mobile station 102 may bemultiplexed onto the channel portion by a statistical multiplexer 116that is part of the radio access network 11. The combined flow of themultiplexed traffic from the mobile stations 100 and 102 are outputtedby the statistical multiplexer 116.

As noted above, in an EGPRS system, each channel portion that is used tocarry traffic from a mobile station includes one of eight time slots ina frame. In the case of the full-rate voice user (or otherconversational traffic class user), the time slot is a dedicated timeslot that is typically not shared with other mobile stations. This isbecause conversational traffic class users are more sensitive to delays.For half-rate users, each time slot is allocated to two mobile stations,but again, sharing is typically not performed during the allocatedportions of the time slot for each mobile station. However, asubstantial portion of the time slot allocated to a conversational classtraffic mobile station is not used during DTX mode. To take advantage ofthis unused bandwidth, traffic from other mobile stations, such as themobile station 102, can be multiplexed into the silent periods 104, 106,and 108. For optimal performance, the traffic that is multiplexed intothe DTX periods includes traffic that is not sensitive to delays, suchas traffic in the background or interactive traffic class. However, ifdelays associated with the multiplexing are not too excessive,multiplexing of voice traffic data between two conversational trafficclass users may also be performed, in some embodiments.

Referring to FIG. 3, the process by which multiplexing of traffic fromtwo mobile stations is enabled for a channel portion (referred to as“channel portion Y”) in the uplink path (from the mobile station to thebase station 12) and subsequent allocation of the channel portion backto the mobile station is illustrated. The mobile station (“mobilestation A”) sends speech frames (at 302) associated with a user (“userA”) to the base station 12 on channel portion Y. In one embodiment, thecommunication of speech frames occurs during talkspurt mode. When themobile station detects (at 304) that user A has stopped talking, themobile station enters (at 306) DTX mode. When it enters DTX mode, themobile station sends (at 308) a message indicating that DTX mode isstarting or has started. In one embodiment, the message is a SID_FIRSTframe, which is a marker to define the end of speech and the start ofDTX mode. When the base station 12 receives the SID_FIRST frame, thebase station 12 assigns (at 310) channel portion Y to another mobilestation (“mobile station B”). At this point, mobile station A is silentwhile mobile station B is transmitting on the uplink channel portion Y.

During DTX mode, mobile station A keeps its uplink TFI (temporary flowidentifier) of a TBF (temporary block flow). Normally, the TFI is usedto identify one of multiple users on the same channel portion (forinteractive or background class traffic, for example). Under EGPRS, theTFI is a 5-bit value, thus enabling up to 32 users on the same channelportion. Although mobile station A maintains its TFI value, radioresources of channel portion Y can be allocated to another mobilestation. Also, the packet timing advance control channel (PTCCH) that isassigned to mobile station A can be relinquished to the other user.

However, although radio resources have generally been relinquished tomobile station B during DTX mode of mobile station A, control messagesfor maintenance purposes are still needed for mobile station A. For thatreason, such control messages are communicated at set periods in theuplink path. The control messages include the SID_UPDATE message, whichis used to communicate comfort noise parameters. Also, during the setperiods, mobile station A can transmit PTCCH (packet timing advancecontrol channel) to maintain time alignment; PACCH (packet associatedcontrol channel) to transmit control messages such as a channel qualitymessage that includes parameters for link adaptation; RTCP (Real-TimeProtocol Control Protocol) messages to provide feedback on the qualityof real-time data communicated in the downlink path; and RSVP (ResourceReserVation Protocol) Time Values objects to refresh the QoS path in thenetwork. RTP is described in RFC 1889, entitled “RTP: A TransportProtocol for Real-Time Applications,” dated January 1996; and RSVP isdescribed in RFC 2205, entitled “Resource ReSerVation Protocol: Version1 Functional Specification,” dated September 1997.

At a later point in time, mobile station A detects (at 312) that user Ahas started talking again. As a result, mobile station A sends (at 314)an indication to the base station 12 that mobile station A again needschannel portion Y. In one embodiment, the message is in the form of anRTFACCH resource request message (RTRRM) sent by mobile station A to thebase station 12. RTFACCH can also be used to carry an uplink assignmentmessage (RTUAM), which is transmitted by the base station 12 (at 316) inresponse to RTRRM to assign uplink radio resources to mobile station A.Upon receipt of the RTUAM, mobile station A enters into talkspurt modeand again transmits (at 318) speech frames on channel portion Y.

In one embodiment, a speech traffic frame (or another type of real-time,interactive data frame) of a full-rate mobile station is interleavedover bursts in eight frames (or eight bursts). However, a speech trafficframe of a half-rate mobile station is interleaved over four bursts.

Referring to FIGS. 4A-4B, according to one embodiment, the interleavingscheme for half-rate mobile stations (mobile station A and mobilestation B) are illustrated. Mobile station A is referred to as mobilestation U1 in FIGS. 4A-4B, while mobile station B is referred to asmobile station U2 in FIGS. 4A-4B. Also, the statistical multiplexing oftraffic from another mobile station (which can be a full-rate mobilestation referred to as mobile station C or mobile station U3 in FIGS.4A-4B) during DTX of one of the mobile stations A and B is alsoillustrated. In one embodiment, a multiframe 700 in the uplink path anda multiframe 702 in the downlink path carry control and traffic frames.Each of the multiframes 700 and 702 includes 52 frames FN0-FN51. Eachframe has eight time slots TN0-7. In the example shown, time slot TN0 isassigned to carry speech associated with half-rate mobile stations A andB. For purposes of illustration, each mobile station transmits a streamof speech traffic frames SF #i, i=0 to M (that is, SF #0, . . . , SF#M). In accordance with some embodiments of the invention, theinterleaving scheme for a speech traffic frame (SF #i) uses a firstinterleaving algorithm for a first set of traffic frames and a secondinterleaving algorithm for a second set of traffic frames. The first setof traffic frames can be the odd set (that is, i=1, 3, 5, etc.), whilethe second set of traffic frames can be the even set (that is, i=0, 2,4, etc.).

The first and second interleaving algorithms are designed to enablestatistical multiplexing of traffic from a half-rate mobile station andtraffic from another mobile station (which can be a full-rate mobilestation that is transmitting best effort data such as interactive orbackground class data). The best effort data is typically interleavedover four bursts, while speech data for a half-rate mobile station isinterleaved over four bursts of two blocks.

Each multiframe 700 or 702 includes plural blocks, with each blockcontaining four frames. FIGS. 4A-4B show the interleaving scheme usedfor half-rate mobile stations A and B. In the illustrated example, inthe uplink path, speech frame SF#n (with n being an even number) formobile station A is interleaved over four bursts in frames FN1-3 inblock B0 (including frames FN0-3) and frame FN8 in block B2 (includingframes FN8-11). The next speech frame SF#n+1 (n+1 being an odd number)is interleaved over four bursts in frame FN3 in block B0 and framesFN8-10 in block B2.

Similarly, speech frame SF#k (with k being an odd number) for mobilestation B is interleaved over four bursts in frames FN5-7 in block B1(including frames FN4-7) and frame FN13 in block B3 (including framesFN13-16). Speech frame SF#k+1 (with k+1 being an odd number) isinterleaved over four bursts in frame FN7 in block B1 and frames FN13-15in block B3.

Thus, generally, when a speech frame starts on block B(x), the i^(th)speech frame is interleaved over B(x+2k) and B(x+2k+2), where k is equalto INT(i/2). The operation INT(y) involves taking the integer value ofy. If the value of i is even, then speech frame SF#i is interleaved overbursts in the last three frames in block B(x+2k) and the first frame inblock B(x+2k+2). If the value of i is odd, then speech frame SF#i isinterleaved over bursts in the last frame of block B(x+2k) and the firstthree frames in block B(x+2k+2).

The interleaving scheme discussed above for half-rate mobile stationsenables statistical multiplexing in a channel portion (in this exampletime slot TN0 of each frame) of traffic from a half-rate mobile stationand traffic from another mobile station. This is accomplished byensuring that each SID_FIRST frame (which is interleaved over fourbursts) is contained in the same block that carries the last speechtraffic frame.

In the example of FIGS. 4A-4B, the last speech frame for mobile stationA (before DTX) is SF#n+1, which is interleaved over blocks B0 and B2.The SID_FIRST frame (represented as “F” in FIGS. 4A-4B) is also carriedin block B2, and is interleaved over bursts in the last three framesFN9-11 of block B2. Thus, mobile station A stops traffic transmissionafter block B2, while mobile station B continues to transmit speechtraffic. Frame FN12 is used to carry the PTCCH (Packet Timing AdvancedControl Channel) between blocks B3 and B4.

Once mobile station A has entered into DTX mode, time slot TN0 in thesubsequent block that would have been allocated to mobile station A(block B5) is allocated to another mobile station C to carry traffic ofmobile station C. The frames carrying traffic of mobile station C aremarked with “U3: DATA”. The next block B6 is used to carry the speechtraffic for mobile station B.

After the idle frame FN25, frames FN26-29 (block B7) are used to carrytraffic transmitted by mobile station C. Next, in frames FN30-33 (blockB8), the speech traffic for mobile station B is communicated.

In accordance with some embodiments, even though mobile station A is inDTX mode, it continues to transmit SID_UPDATE messages to convey comfortnoise parameters. The SID_UPDATE message is interleaved over bursts inframe numbers FN34-37 (block B9). In one embodiment, the SID_UPDATEmessage is communicated by the mobile station in DTX mode every (N+1)thradio block, where N is set to some arbitrary value, e.g., N greaterthan or equal to 1. In the example illustrated in FIGS. 4A-4B, N isequal to 2. Also, at longer intervals, the same (N+1)th radio block mayalso be used for the following purposes: transmitting PTCCH informationperiodically; transmitting control messaging through PACCH; transmittingRTCP packets through PDTCH; and transmitting RSVP Time Values objectsthrough PDTCH.

After block B9, the next frame FN38 carries PTCCH information, followedby traffic from the mobile station B in frames FN39-42 (block B10). Thenext block B11 is used to carry traffic for mobile station C. Also, atthis time, mobile station A has detected user voice traffic again andwishes to begin re-transmitting. To do so, mobile station A transmitsRTRRM (represented by R) in frame FN45 (which is also carrying trafficfrom the mobile station C).

Generally, according to one embodiment, RTRRM can be transmitted on anyframe number of a multiframe except the following: FN mod 52=12 (whichcarries PTCCH), 25 (which is idle), 38 (which carries PTCCH), or 51(which is idle).

In response to RTRRM in frame FN41, the base station transmits RTUAM(represented as A) in frame FN46 of multiframe 702 (on the downlink).With RTUAM, the base station allocates time slot TN0 in the multiframe700 back to mobile station A. After being allocated back time slot TN0,mobile station A transmits the ONSET frame (not shown in FIGS. 4A-4B) toindicate that the beginning of a speech frame is about to begin and tore-start traffic transmission.

On the downlink path, statistical multiplexing of traffic destined fortwo different mobile stations can also be performed. However, since thebase station is aware of when it has entered DTX mode with one mobilestation, it can easily multiplex the traffic from another mobile stationduring its silence period with the first mobile station. The RTFACCHmechanism discussed for the uplink path is not required to performstatistical multiplexing on the downlink path. Thus, while mobilestations A and B are transmitting speech frames on the uplink path inbursts in frames FN0-7 (blocks B0 and B1), the base station is nottransmitting data on the downlink path, and thus the base station entersDTX mode on the downlink path to mobile stations A and B. During thisdownlink DTX period, frames FN0-1 can be used to communicate traffic toanother mobile station (e.g., mobile station C or U3). Although theexample shows traffic of mobile station C being carried during DTXperiods of the base station on the downlink path to mobile stations Aand B, it should be noted that the traffic can be from another mobilestation.

SID_UPDATE frames are communicated on the downlink path from the basestation to mobile station A on frames FN8-11 (block B3) of themultiframe 702. Next, the base station transmits downlink traffic tomobile station C in frames FN13-16. After the base station allocatestime slot TN0 back to mobile station A, the base station transmits theONSET frame in frames FN17-19 in block B5, along with a portion ofspeech frame 0 (SF#0) in frames FN18-20. Pursuant the interleavingscheme discussed above, the remainder of speech frame SF#0 to mobilestation A is communicated in block B7 (in frame FN26). Since thedownlink path to mobile station B is still in DTX mode, that portion oftime slot TN0 can be used to carry traffic to mobile station C. Formobile station A, subsequent speech frames SF#1, SF#2, and SF#3 areinterleaved over bursts in frames of blocks B7 and B9. In addition, SF#3is the last traffic frame, so a SID_FIRST frame is also interleaved overbursts in block B9 to indicate the start of DTX mode.

Next, blocks B10-B12, are used to carry traffic targeted for mobilestation C since the downlink paths from the base station to both mobilestations A and B are now silent. However, the base station also detectstransmission of the RTRRM message in block B11 at this time (transmittedby mobile station A in frame FN45). In response to detection of RTRRM,the base station preempts the transmission of traffic for mobile stationC in frame FN46 and transmits RTUAM instead.

FIGS. 4A-4B illustrate a first interleaving scheme for the SID_FIRSTframe for when the last speech traffic frame is an odd burst (SF#n+1 inthe example). The SID_FIRST frame is interleaved according to adifferent scheme when last speech traffic frame is an even frame, whichis illustrated in FIGS. 5A-5B.

As shown in FIGS. 5A-5B, the last speech frame for mobile station A isSF#n (n being an even number), which is interleaved over frames FN1-3 inblock B0 and FN8 in block B2. In this scenario, the SID_FIRST frame isinterleaved over frame FN3 in block B0 and frames FN8-9 in block B2.Also, the SID_FIRST frame is repeated in frames FN10-11.

Thus, generally, the SID_FIRST frame has the following interleavingscheme. When the last speech frame interleaved is even (that is, i iseven) and sent on block B(x), then SID_FIRST is interleaved over thelast burst of block B(x) and the first two bursts of block B(x+2).Subsequently, the SID_FIRST frame is repeated in the last two frames ofblock B(x+2). When the last speech frame is odd, the SID_FIRST frame isinterleaved over the last three bursts of block B(x).

The downlink multiframe 702 shown in FIGS. 5A-5B contains the same dataas that in FIGS. 4A-4B.

FIGS. 4A-4B and 5A-5B illustrate examples for half-rate mobile stations.The statistical multiplexing mechanism for a full-rate mobile stationthat enters DTX mode is described below in connection with FIGS. 6A-6Band 7A-7B. Referring to FIGS. 6A-6B, a multiframe 710 communicated inthe uplink path and a multiframe 712 communicated in the downlink pathare illustrated. The multiframes 710 and 712 each includes 52 framesFN0-FN51. According to one configuration, a speech frame (SF) of afull-rate mobile station is interleaved over eight bursts. In theexample shown in FIGS. 6A-6B, time slot TN0 is assigned to carry speechassociated with a first mobile station (mobile station A), which is afull-rate mobile station. Thus, as shown, speech frame 1 (SF#1) isinterleaved over bursts in frames FN0-7 (blocks B0 and B1). The lasthalf of speech frame 0 (SF#0) is interleaved over bursts in framesFN0-3. Speech frame 2 (SF#2) is interleaved over bursts in frames 4-11(blocks B1 and B2). SF#2 is the end of speech stream from the firstmobile station, so that SID_FIRST (F) frames are also interleaved overbursts in frames FN8-11 (block B3). Frame FN12 is used to carry thePTCCH (Packet Timing Advanced Control Channel).

Since the first mobile station (mobile station A) has entered into DTXmode, time slot TN0 in the subsequent frames of the multiframe can beallocated to a second mobile station (mobile station B), also afull-rate mobile station, to carry traffic transmitted by mobile stationB. As shown, traffic associated with mobile station B is carried inframes FN13-20 (blocks B4 and B5). The frames carrying traffic of mobilestation B are marked with “MB”.

In accordance with some embodiments, even though the first mobilestation is in DTX mode, it continues to transmit SID_UPDATE messages toconvey comfort noise parameters. The SID_UPDATE message is interleavedover frame numbers FN21-24 (block B6). In one embodiment, the SID_UPDATEmessage is communicated by the mobile station in DTX mode every (N+1)thradio block, where N is set to some arbitrary value, e.g., N greaterthan or equal to 1. In the example illustrated in FIGS. 6A-6B, N isequal to two. Also, at longer intervals, the same (N+1)th radio blockmay also be used for the following purposes: transmitting PTCCHinformation periodically; transmitting control messaging through PACCH;transmitting RTCP packets through PDTCH; and transmitting RSVP TimeValues objects through PDTCH.

After the idle frame FN25, frames FN26-33 (blocks B7 and B8) are used tocarry traffic transmitted by mobile station B. Next, in frames FN34-37(block B9), the SID_UPDATE frame is transmitted by the mobile station A.The next frame FN38 carries PTCCH information, followed by traffic fromthe mobile station B in frames FN39-42 (block B10). In addition, at thistime, mobile station A has detected user voice traffic again and wishesto begin re-transmitting. To do so, mobile station A transmits RTRRM(represented by R) in frame FN41 (which is also carrying traffic fromthe mobile station B).

As in the case with half-rate mobile stations in the examples of FIGS. 4and 5, RTRRM can be transmitted on any frame number of a multiframeexcept the following: FN mod 52=12 (which carries PTCCH), 25 (which isidle), 38 (which carries PTCCH), or 51 (which is idle).

In response to RTRRM in frame FN41, the base station transmits RTUAM(represented as A) in frame FN42 of multiframe 712 (on the downlink).With RTUAM, the base station has allocated time slot TN0 in themultiframe 710 back to mobile station A. After being allocated back timeslot TN0, mobile station A transmits the ONSET frame in frames FN43-46(block B11). Mobile station A also starts transmitting speech frame 0(SF#0) after exiting DTX mode. SF#0 is interleaved over eight framesFN43-50 (blocks B11 and B12). Mobile station A continues to transmitfurther speech frames.

On the downlink path, statistical multiplexing of traffic destined fortwo different mobile stations can also be performed. However, since thebase station is aware of when it has entered DTX mode with one mobilestation, it can easily multiplex the traffic from another mobile stationduring its silence period with the first mobile station. The RTFACCHmechanism discussed for the uplink path is not required to performstatistical multiplexing on the downlink path. Thus, while mobilestation A is transmitting speech frames on the uplink path in framesFN0-7 (blocks B0 and B1), the base station is not transmitting data onthe downlink path, and thus the base station enters DTX mode on thedownlink path to mobile station A. However, the same frames can be usedto communicate traffic to another mobile station (e.g., mobile stationB). SID_UPDATE frames are communicated on the downlink path from thebase station to mobile station A on frames FN8-11 (block B3) of themultiframe 712. After the base station allocates time slot TN0 back tomobile station A, the base station transmits the ONSET frame in burstsFN13-16 (B4), along with speech frame 0 (SF#0). Further speech framesare communicated in subsequent frames of the multiframe 712, until thespeech has stopped. At that point, in frames FN34-37 (block B9), theSID_FIRST frame is transmitted downlink in bursts in frames FN34-37.

Next, the block (B10) starting at frame FN39 is used to carry traffictargeted for mobile station B since the downlink path from the basestation to the first mobile station is now silent. However, the basestation also detects transmission of the RTRRM message at this time(transmitted by the first mobile station in frame FN41). In response todetection of RTRRM, the base station preempts the transmission oftraffic for mobile station B in frame FN42 and transmits RTUAM instead.

FIGS. 6A-6B illustrate the minimum delay between when an RTRRM messageis transmitted by the mobile station A after the re-establishment ofuplink speech transmission by the first mobile station. In the exampleof FIGS. 6A-6B, a one-frame delay is experienced between RTRRM and thestart of speech transmission in frame FN43 in the uplink multiframe 710.Minimum delays between RTRRM and RTUAM were also illustrated in theexamples of FIGS. 4 and 5 for half-rate mobile stations.

Referring to FIGS. 7A-7B, a maximum delay scenario for full-rate mobilestations is illustrated. FIGS. 7A-7B show a multiframe 800 on the uplinkpath and a multiframe 802 on the downlink path. The difference betweenthe examples of FIGS. 6A-6B and 7A-7B is that RTRRM is transmitted inframe FN42 in the multiframe 800 (instead of frame FN41 in themultiframe 710 of FIGS. 6A-6B). Frame FN42 is the last frame of blockB9. As a result, the assignment message RTUAM is not communicated untilthe beginning of the next block (B10) in frame FN43. As a result, thenext block B10 on the uplink path is not allocated to the first mobilestation (so that traffic from mobile station B continues to betransmitted in the uplink multiframe 800). It is not until block B11 ofthe uplink multiframe 800 that mobile station A can resume transmissionof traffic in time slot TN0.

Referring to FIGS. 8A-8B, some of the components of the mobilecommunications system 10 of FIG. 1 are illustrated in greater detail. Amobile station 200 communicates over a wireless link with a base station202, which has a Iu-ps interface 236 that is coupled to the SGSN 50. Themobile station 200 includes an RF transceiver 227 that is connected toan RF antenna 228. The mobile station 200 also includes an RLC/MAC(radio link control/medium access control) layer 225. The RLC moduleprovides a radio-solution-dependent reliable link, and the MAC modulecontrols the access signaling (request and grant) procedures for theradio channel.

The RLC/MAC layer 225 also includes a transmit DTX (TX DTX) handler 220that passes traffic frames to a TX RSS (transmit radio subsystem) 222 inthe transceiver 227. Each frame passed to the TX RSS 222 includes bitfields containing the information bits, the audio coder/decoder (CODEC)mode indication, and a TX_TYPE identifier to identify the content of theframe. The TX_TYPE identifier can specify that the frame containsspeech; SID_FIRST to mark the end of speech; SID_UPDATE to providecomfort noise parameters; ONSET to indicate that the beginning of aspeech frame is about to begin; NO DATA to indicate that the framecontains no useful data and should not be transmitted over the airinterface; and other information. The transceiver 227 also includes anRRM generator 223 for generating RTRRM messages. As will be discussedfurther below, an RTRRM message is a coded version of the TFI associatedwith the mobile station. The RRM generator 223 performs the coding inaccordance with some embodiments.

The TX DTX handler 220 includes a voice activity detector to assesswhether input signals contain speech or not. If there is no speech, thenthe TX DTX handler 220 sends an indication to the TX RSS 222 to enterDTX mode by setting the flag TX_TYPE to the value corresponding toSID_FIRST. When the TX RSS 222 receives a SID_FIRST frame, radiotransmission from the TX RSS 222 is cut off. The TX DTX handler 220receives audio data from an audio CODEC 270, which is coupled to ananalog-to-digital (A/D) and digital-to-analog (D/A) converter 272 thatoutputs audio data to a speaker 274 and receives input audio from amicrophone 276.

During DTX mode, the TX RSS 222 is resumed at regular intervals fortransmission of SID_UPDATE frames to communicate comfort noiseparameters calculated in the TX DTX handler 220. The TX RSS 222 includesa channel encoder to encode information to be communicated over the airlink.

Frames received over the air are passed by the transceiver 227 upthrough the RLC/MAC layer 225 and upper layers (not shown). Receivedcontrol messages are processed by the upper layers or by one or moresoftware routines 212. Received speech messages are passed to the audioCODEC 270 for output on the speaker 274.

The statistical multiplexer 116 (FIG. 2) can be implemented in one ormore layers of the base station 200 (e.g., the transceiver 227, RLC/MAClayer 225, and higher layers).

In one configuration, radio access bearer 0 (RABO) is used, in which theRTP/UDP/IP (Real-Time Protocol/User Datagram Protocol/Internet Protocol)header of each speech frame is removed in the radio access network 11 onthe downlink path before transmission to the mobile station. TheRTP/UDP/IP header is then reconstructed by the mobile station. On theuplink path, the RTP/UDP/IP header is removed by the mobile station andthen reconstructed in the radio access network 11. For the radio accessbearer 1 and 2 (RAB1 and RAB2) configurations, the RTP/UDP/IP header(compressed or uncompressed) is communicated to/from by the mobilestation and radio access network 11. To do so, appropriate RTP, UDP, andIP stacks (not shown) are provided in the mobile station.

The various software layers, routines or modules in the mobile station200 are executable on a control unit 208, which is connected to astorage unit 210. The mobile station 200 also includes an input/output(I/O) interface 218, which is connected to a keyboard 214 and a display216.

The base station 202 also includes a transceiver 253 that is coupled toan antenna tower 251 and an RLC/MAC layer 255. The transceiver 253includes a receive radio subsystem (RX RSS) 252 for receiving framesover the air link. The RX RSS 252 is connected to a receive DTX (RX DTX)handler 250 in the RLC/MAC layer 255. The RX DTX handler 250 isresponsible for the overall DTX operation on the receive side. The RXRSS 252 continuously passes received traffic frames to the RX DTXhandler 250. A flag RX_TYPE is set by the RX RSS 252 to indicate how theframe is to be handled by the RX DTX handler 250. For example, theRX_TYPE flag can indicate that the received frame includes speech orthat the received frame includes a SID_FIRST, SID_UPDATE, or ONSETmessage.

The base station 202 includes a radio resource management (RRM) module237 that receives indications (SID_FIRST) that radio resources areavailable for statistical multiplexing because a mobile station has goneidle (e.g., DTX mode). When that occurs, the radio resources, in theform of a channel portion, are allocated to another mobile station forthe uplink.

The base station 202 also includes a fast access module 242 to controlthe RTFACCH operation. The fast access module 242 detects for receipt ofthe RTRRM message, and in response to the RTRRM message, the fast accessmodule 242 sends an RTUAM message to the mobile station 200 to re-assigna channel portion to the mobile station 200. The fast access modulecooperates with one or more base station routines 234 to determineallocation of the channel portion. The fast access module 242 and thesoftware routines 234 are executable on a control unit 230, which iscoupled to a storage unit 234.

In accordance with some embodiments, decoding for presence of RTRRM onthe channel portion is performed by an RTRRM detector 238 in thetransceiver 253. RTRRM is transmitted by the mobile station 200 duringtransmission of actual data traffic by another mobile station on thesame channel portion. The RTRRM detector 238 is discussed in greaterdetail below in connection with FIG. 11.

Referring to FIG. 9, while mobile station 200A (400) is in DTX mode,mobile station 200B (402) is transmitting bursts 406 over the allocatedchannel portion (time slot TNx). To request re-assignment of the channelportion, the mobile station 200A sends the RTRRM frame 408 in the sametime slot that it was assigned during its previous talkspurt mode.However, the mobile station 200A can send RTRRM on a new time slot ifthe radio access network 11 sends PACCH on the downlink during thesilence period of mobile station 200A to indicate a new time slot and/orfrequency assignment.

In accordance with some embodiments, the RTRRM frame 408 includes the5-bit TFI of the mobile station 200A. Normally, the TFI is used toidentify one of multiple users on the same channel portion. In oneembodiment, up to 32 users may be placed on the same channel portion,with the 5-bit TFI identifying one of the 32 users. In one embodiment,the 5 TFI bits are coded into 148 bits and sent over the entire burst408, which in one embodiment is 156.25 symbols long (which correspondsto about 577 microseconds). Each information bit in the burst 408 has aninformation rate fb of about 8.667 kilobits per second (kb/s). In oneexample, the 5 TFI bits are coded by using a maximal length sequence ata chip rate f_(c) equal to the EGPRS symbol rate of about 270.855symbols per second, which results in a coding gain (CG) of 15 dB.

Each of the TFI bits is converted to one of two codes based on the stateof the TFI bit. This coding is performed by the RRM generator 223 (FIG.4A). If the TFI bit has state 0, then the bit is converted to thefollowing 31-bit maximal length (ML) sequence:

Code-0=11110 11100 01010 11010 00011 00100 1.

If the TFI bit has state 1, then the bit is converted to the followingML sequence:

Code-1=11110 11001 11000 01101 01001 00010 1.

Since the TFI after coding results in a total of 155 bits (31×5), not148, 7 bits are “punctured” or truncated. The punctured bits correspondto TFI bits 0 and 4; as a result, TFI bits 0 and 4 get less coding gaincompared to the remaining TFI bits. In other embodiments, other codingschemes may be selected to achieve a more uniform coding gain for allfive bits of TFI. In alternative embodiments, other codes can be used.Also, alternatively, instead of two codes, a single code can be used,with the states of the bits flipped to represent “0” and “1” states.

By using an RTRRM that is one burst in length, a relatively fastmechanism is enabled for re-assignment of the requested time slot backto the mobile station 200A. Also, to ensure reliable detection, RTRRM istransmitted at relatively high power, up to the maximum power permittedfor the mobile station 200A. The transmission of the RTRRM burst 408overlaps and coincides with the data traffic bursts 406 transmitted bythe mobile station 402. To detect the presence of RTRRM despite thiscollision, the RTRRM detector 238 in the base station 202 uses jointdetection or successive cancellation techniques, as further describedbelow. Optionally, RTRRM may also be independently detected.

Collision between the RTRRM burst 408 and the traffic burst 406 may ormay not cause the traffic burst 406 to be corrupted. If the trafficburst 406 is corrupted, then the base station 202 may requestretransmission of the traffic burst 406 from the mobile station 200B. Ifthe traffic burst 406 from the mobile station 200B contains speech data,then a speech frame substitution technique may be used to recovercorrupted speech data. In one example, the speech frame substitutiontechnique involves substituting a previously received speech frame inplace of the present frame if the present frame is corrupted.

Referring to FIG. 10, one embodiment of an RTUAM burst 500 isillustrated. The RTUAM burst 500 includes a header portion 502 thatidentifies the burst 500 as an RTUAM. The body of the RTUAM burst 500includes the following: <TFI>, which represents the five-bit TFI;{0|1<Uplink_TFI_ASSIGNMENT>}, which is used by the radio access network11 to assign another TFI to the mobile station exiting DTX mode so thatthe mobile station transmits on a different time slot and/or RFfrequency; <TSC>, which represents the training sequence code used formeasuring co-channel interference; <ARFCN>, which represents the radiofrequency of the channel assigned to the mobile station;<TIMESLOT_ALLOCATION>, which contains the time slot assignment for themobile station; and padding bits.

The RTUAM burst 500 is one burst in length to decrease the delay inre-assigning a time slot back to a mobile station exiting DTX mode. Thisis particularly important for mobile stations communicatingconversational class traffic, which are the most sensitive to delay ofthe four possible traffic classes. To prevent collision between theRTUAM burst 500 and other data on the downlink, the base station willpreempt transmission of any other data on the downlink. To improvereliability in detection of RTUAM, repetition diversity may be employed,as explained below. Also, in further embodiments, an RTUAM burst havinga larger length may be employed to improve reliability.

Referring to FIG. 11, processing of various messages by the base stationis illustrated. If the base station detects receipt of a robust AMR(adaptive multi-rate) traffic synchronized control channel (RATSCCH),the base station decodes the RATSCCH frame (at 604). The RATSCCH frameis used to convey RATSCCH messages and to change CODEC configurations onthe radio interface. The RATSCCH frame is passed to the RX DTX handler250 as a NO_DATA frame.

If the base station detects (at 606) receipt of a SID_FIRST frame, theframe is passed to the RX DTX handler 250 as the SID_FIRST frame (at608). In addition, the radio resource management (RRM) module 237 isnotified that uplink radio resource is now available for statisticalmultiplexing. The base station also begins looking for an RTRRM burst,and if an RTRRM burst is received, a responsive RTUAM burst istransmitted to the mobile station.

The base station can also detect a SID_UPDATE frame (at 610). Inresponse, the frame is decoded and passed (at 612) to the RX DTX handler250 as SID_UPDATE, SID_BAD or NO_DATA frame depending on the CRC (cyclicredundancy check) and the content of information bits along with comfortnoise parameters. Also, the base station checks to determine if thereceived message is a PACCH burst, PTCCH burst, or a PDTCH (packet datatraffic channel) burst (containing RTCP or RSVP signaling). The purposesof these messages are discussed above. The base station continues tomonitor for the RTRRM message, and if the RTRRM burst is detected, aresponsive RTUAM burst is transmitted.

The base station can also detect (at 614) an ONSET frame, which ispassed (at 616) to the RX DTX handler 250 as an ONSET frame. Thisindicates that an RTRRM burst has been detected, that the RTUAM has beentransmitted in response to the RTRRM, and the RRM module 237 has beennotified that the uplink radio resource is no longer available forstatistical multiplexing.

If none of the RATSCCH, SID_FIRST, SID_UPDATE, and ONSET frames aredetected, then the base station decodes (at 618) the received frame as aspeech frame. If the SID_FIRST frame has been previously detected withno subsequent detection of the ONSET frame, then the base stationcontinues to monitor for the RTRRM message.

In an EGPRS system, multiframes are used to communicate control andtraffic signaling between mobile stations and base stations. Themultiframes can include 52 frames, with each frame containing eight timeslots. A multiframe starts with frame FN0 and ends with frame FN51. Fourframes make up a block. Generally, conversational traffic is interleavedover eight frames, while traffic in the other traffic classes isinterleaved over four frames.

Referring to FIG. 12, the relative timing between RTRRM, RTUAM, andresumption of uplink transmission is illustrated, given different timesat which RTRRM is sent. A downlink stream 900 and an uplink stream 902of frames are illustrated. In the example of FIG. 12, time slot TN1 isthe time slot used for communications by a first mobile station (mobilestation A). As shown in FIG. 12, the uplink stream is delayed withrespect to the downlink stream by three time slots. The stream isdivided into three blocks Bx, Bx+1, and Bx+2. Assuming that mobilestation A is in the DTX mode, there are four different possible timeperiods within a block that the first mobile station can transmit RTRRMto request the channel back. In a first scenario, the RTRRM can be sentin the last burst (or time slot) of a block Bx (as indicated by 904).When this occurs, the RTUAM is not transmitted on the downlink (at 912)by the base station in the downlink path until the next block (Bx+1). Inthe next scenario, RTRRM can be transmitted in the uplink in the firstburst of a block (Bx+1) (as indicated at 906). RTRRM can also betransmitted in the second and third bursts of block Bx+1 (as indicatedby 908 and 910, respectively).

With RTRRM transmitted in the uplink path at 904 (the last burst ofblock Bx), the responsive RTUAM message is communicated in the firstburst of the next block Bx+1 (as indicated by 912). However, fortransmissions of RTRRM in the first, second and third bursts of blockBx+1 (906, 908, and 910, respectively), the RTUAM is communicated in thelast burst of block Bx+1 (as indicated by 914) so that the base stationhas at least two or more bursts to detect the presence/absence of RTRRMon the uplink. In response to communication of RTUAM at 912 or 914,uplink traffic transmission from the first mobile station can resume inthe first burst of the next block (Bx+2), as indicated by 916.

For improved reliability in detection of RTRRM, repetition diversity maybe used, in which RTRRM is transmitted multiple times. This is possiblewhen RTRRM is transmitted in the first or second bursts of a block (suchas at 906 and 908 in FIG. 10). To enable repetition of RTRRM, RTUAM istransmitted in the last burst of the block.

Repetition diversity can also be used for RTUAM by sending it atdifferent times. For example, if RTUAM is sent in the first burst of ablock, then RTUAM may be repeated three more times. The plural RTUAMbursts are independent of each other (each is self-sufficient), and theymay employ different parity protection to enhance error protection.However, if RTUAM is sent on the third or fourth burst of a block, thenthe base station may not be able to perform repetition diversity forRTUAM.

In accordance with some embodiments of the invention, the joint 238detector (FIGS. 8A-8B) is used to simultaneously decode both RTRRM froma first mobile station and traffic from a second mobile station. Asnoted above, RTRRM comprises the 5-bit downlink TFI coded into 148 bits.The kth sample of the complex envelope of the received signal at theoutput of a base station receiver filter, r(kT) represented as r_(k) canbe expressed as follows, when RTRRM is not present:

$\begin{matrix}{r_{k} = {{\sum\limits_{i = 0}^{L - 1}{c_{i}s_{k - i}}} + {\sum\limits_{i = 0}^{N - 1}{e_{i}I_{k}^{(i)}}} + n_{k}}} & \left( {{Eq}.\mspace{14mu} 1} \right)\end{matrix}$

However, when RTRRM is present, r_(k) is expressed as follows:

$\begin{matrix}{r_{k} = {{\sum\limits_{i = 0}^{L - 1}{c_{i}s_{k - i}}} + {\sum\limits_{i = 0}^{L - 1}{d_{i}p_{k - i}}} + {\sum\limits_{i = 0}^{N - 1}{e_{i}I_{k}^{(i)}}} + n_{k}}} & \left( {{Eq}.\mspace{14mu} 2} \right)\end{matrix}$

In Eqs. 1 and 2 above, the value s_(k) is the kth sample of theinformation signal from the mobile station B. The value p_(k) is the kthsample of the RTRRM signal from the mobile station A, and n_(k) is thekth sample of the receiver noise. Also, I_(k) ^((i)) represents the kthsample of the ith interferer, {c_(i)} and {d_(i)} represent the channelimpulse responses associated with mobile stations A and B, respectively.L is the length (in symbols) of the channel impulse response, and Nrepresents the number of cochannel interferers. {ei} is the channelweight associated with the ith interferer. Here, it is assumed that theinterferer is passed through a flat fading channel.

In a given maximum likelihood sequence estimator (MLSE), the jth branchmetric, γ_(k) ^((j)), at time instant k, is calculated in the absence ofRTRRM as follows:

$\begin{matrix}{\gamma_{k}^{(i)} = {{r_{k} - {\sum\limits_{i = 0}^{L - 1}{{\hat{c}}_{i}{F\left( I^{({i\rightarrow j})} \right)}}}}}^{2}} & \left( {{Eq}.\mspace{14mu} 3} \right)\end{matrix}$

where F(I^((i→j))) represents the symbol vector of traffic from mobilestation A resulting from the transition from the ith state at time (k−1)to the jth state at time k. {ĉ_(j)} represents the estimated channelimpulse response.

The branch metric is modified to jointly decode the RTRRM from mobilestation A and data from mobile station B as follows:

$\begin{matrix}{\gamma_{k}^{({j,m})} = {{r_{k} - {\sum\limits_{i = 0}^{L - 1}{{\hat{c}}_{i}{F\left( I^{({i\rightarrow j})} \right)}}} - {\sum\limits_{i = 0}^{L - 1}{d_{i}{F\left( {{Code} - m} \right)}}}}}^{2}} & \left( {{Eq}.\mspace{14mu} 4} \right)\end{matrix}$

where the third term on the right-hand side of Eq. 4 corresponds toRTRRM and has two possible states (m=0 or 1) corresponding to each ofthe two code waveforms (code-0 and code-1). Additionally, operationsperformed in decoding RTRRM include channel estimation during trainingsequence, {{circumflex over (d)}_(i)}, calculation of the branch metriccorresponding to RTRRM for each of the two code waveforms (m=0 and 1),and determination of the downlink TFI of the MS TBF.

In one arrangement, the third term on the right-hand side of Eq. 4 canbe calculated on a continuous basis to check for the presence of RTRRM.However, in another arrangement, the third term of the right-hand sideof Eq. 4 does not need to be continuously calculated to reduceprocessing load. In this other arrangement, the third term on theright-hand side of Eq. 4 is calculated only when it has been determinedthat RTRRM is present. One example of the detector 238 configuredaccording to the latter arrangement is illustrated in FIG. 13. Receivedsignal samples are inputted to a receive filter 1002. The output of thereceiver filter 1002 is provided to a demodulator 1006 and an RTRRMswitch control module 1004. The RTRRM switch control module 1004 detectsfor the presence or absence of RTRRM in the received signal. When theswitch control module 1004 detects the presence of RTRRM, it activatesan RTRRM switch 1008, so that the metric for RTRRM (1010) can beprovided to the demodulator 1006 to decode for RTRRM. Thus, in theexample of FIG. 13, if the received signal does not contain RTRRM, thedemodulator 1006 decodes the received signal into data (associated withmobile station B). However, if the received signal contains RTRRM, thenthe demodulator 1006 decodes RTRRM for use in the base station.

The operations, tasks, and functions discussed herein that are performedin stations or systems in the mobile communications network 10 may becontrolled by software applications, routines, or modules executable oncontrol units, such as those shown in FIGS. 8A-8B. Each control unitincludes a microprocessor, microcontroller, processor card (includingone or more microprocessors or microcontrollers), or another control orcomputing device. As used here, a “controller” or a “control module”refers to hardware, software, or a combination thereof. A “controller”or “control module” can refer to a single component or to multiplecomponents (hardware or software).

The storage units referred to herein include one or moremachine-readable storage media for storing data and instructions. Thestorage media include different forms of memory including semiconductormemory devices such as dynamic or static random access memories (DRAMsor SRAMs), erasable and programmable read-only memories (EPROMs),electrically erasable and programmable read-only memories (EEPROMs), andflash memories; magnetic disks such as fixed, floppy and removabledisks; other magnetic media including tape; and optical media such ascompact disks (CDs) or digital video disks (DVDs). Instructions thatmake up the various software routines or modules in a station or systemand stored in a respective storage unit when executed by a control unitcause the corresponding station or system to perform programmed acts.

The instructions of the software routines or modules are loaded ortransported into the station or system in one of many different ways.For example, code segments including instructions stored on floppydisks, CD or DVD media, a hard disk, or transported through a networkinterface card, modem, or other interface device are loaded into thestation or system and executed as corresponding software routines ormodules. In the loading or transport process, data signals that areembodied in carrier waves (transmitted over telephone lines, networklines, wireless links, cables, and the like) communicate the codesegments, including instructions, to the station or system. Such carrierwaves are in the form of electrical, optical, acoustical,electromagnetic, or other types of signals.

While the invention has been disclosed with respect to a limited numberof embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover such modifications and variations as fall within the truespirit and scope of the invention.

1. A method of interleaving speech data communicated with a particularmobile station over a plurality of frames, comprising: receiving, by asystem from the particular mobile station in a communications sessionover a wireless channel, a first set of the speech data, wherein thefirst set of speech data has been interleaved by the particular mobilestation according to a first algorithm over a first set of pluralframes, wherein a first frame in the first set is spaced apart from asecond frame in the first set by at least one other frame not in thefirst set; and receiving, by the system from the particular mobilestation in the communications session over the wireless channel, asecond set of the speech data, wherein the second set of speech data hasbeen interleaved by the particular mobile station according to a second,different algorithm over a second set of plural frames.
 2. The method ofclaim 1, wherein the speech data interleaved according to the first orsecond algorithm comprises speech data interleaved over frames of amultiframe.
 3. The method of claim 2, wherein interleaving over framesof the multiframe comprises interleaving over a General Packet RadioService multiframe.
 4. The method of claim 2, wherein the multiframecomprises plural blocks and each block comprises plural frames, eachframe containing plural bursts, the speech data being carried in dataframes interleaved over bursts in the plural frames, the method furthercomprising: receiving an end-of-data indicating frame to indicate that adata frame is the last data frame, wherein the end-of-data indicatingframe is interleaved according to predetermined algorithms, wherein thedata frames interleaved according to the first and second algorithms andthe end-of-data indicating frame interleaved according to thepredetermined algorithms enable the end-of-data indicating frame to endwithin the same block carrying the last data frame.
 5. The method ofclaim 2, wherein the multiframe comprises plural blocks, each of theplural blocks having multiple frames.
 6. The method of claim 5, whereinselection of interleaving according to the first algorithm or the secondalgorithm is based on which block of the multiframe a particular set ofspeech data starts on.
 7. A method of interleaving speech data over aplurality of frames, comprising: interleaving, by a half-rate mobilestation, a first set of the speech data according to a first algorithmover a first set of plural frames for communication over a wirelesschannel in a communications session, wherein a first frame in the firstset is spaced apart from a second frame in the first set by at least oneother frame not in the first set; interleaving, by the half-rate mobilestation, a second set of the speech data according to a second,different algorithm over a second set of plural frames for communicationover the wireless channel in the communications session; andtransmitting, by the half-rate mobile station, the interleaved first andsecond sets of speech data to a radio network over the wireless channelin the communications session.
 8. The method of claim 7, wherein thefirst and second sets of speech data are interleaved over frames of amultiframe.
 9. The method of claim 8, wherein the multiframe comprisesplural blocks, each of the plural blocks having multiple frames.
 10. Themethod of claim 9, further comprising: selecting between using the firstalgorithm and the second algorithm to interleave a particular set ofspeech data based on which block of the multiframe a particular set ofspeech data starts on.
 11. A system for communicating over a wirelesschannel in a mobile communications network, comprising: an interface toreceive speech data from a mobile station; and at least one processorto: process a first set of speech data that has been interleaved by themobile station according to a first algorithm over a first set of pluralframes, wherein a first frame in the first set is spaced apart from asecond frame in the first set by at least one other frame not in thefirst set; and process a second set of speech data that has beeninterleaved by the mobile station according to a second, differentalgorithm over a second set of plural frames.
 12. The system of claim11, wherein the speech data interleaved according to the first or secondalgorithm comprises speech data interleaved over frames of a multiframe.13. The system of claim 12, wherein the multiframe comprises pluralblocks, each of the plural blocks having multiple frames.
 14. The systemof claim 13, wherein selection of interleaving according to the firstalgorithm or second algorithm is based on which block of the multiframea particular set of speech data starts on.